he cell biology, biochemistry and immunology of Leishmania and rypanosoma are investigated as models of intra- and xtracellular parasitism, respectively. As all interactions etween host and parasite occur, at least temporarily, at the evel of the parasite surface membrane, emphasis is placed on: ) integrated structural, biochemical and antigenic haracterization of the intact and isolated parasite surface embrane (SM) and parasite released products and 2) defining he mechanisms by which parasites survive and circumvent ost-defense systems. To those ends, various studies are mployed involving: Subcellular fractionation, radiolabeling, lectrophoresis and chromatography assays, immuno-binding and abeling assays and in vitro culture. sing such techniques, the major SM components/antigens of eishmania sp. were identified. The major SM antigens to which eishmaniasis patients make IgG responses were delineated. otal lipid composition of Leishmania SM was determined and 3 M phospholipases characterized. The SM origin and haracterization of Leishmania-released antigens was emonstrated. Antibodies, C-DNA and genomic libraries were ade for isolation of SM antigens and their genes. The inetics and mechanisms of Leishmania SM sugar and amino acid ransport were delineated. Both a SM-proton pump and a pecific [H+]-ATPase were identified. The former providing the lectro-chemical potential for SM transport in this organism. hese results underscore the relevance of the parasite surface embrane and the need for its biochemical and immunochemical haracterization. he goals of this project are to provide fundamental bases for nderstanding the mechanisms of parasite survival.